1. Field of the Invention
This invention is related to integrated circuits and, more particularly, to register files and other memory circuits in an integrated circuit.
2. Description of the Related Art
As integrated circuit fabrication process technology has continued to progress, reducing the feature sizes of transistors with each new process node, the supply voltage to the integrated circuit has also continued to decrease. Additionally, as the operating frequencies increase (made possible in part by the continued process technology advancement), the reduced supply voltage has contributed to reduced power consumption.
However, one limit to the reduction of supply voltage that is experienced in integrated circuits that integrate memories (such as SRAM) is related to the robustness of the memory. As supply voltage decreases below a certain voltage, the ability to reliably read and write the memory decreases. The reduced reliability may have several sources. The resistances of some devices in the memory (e.g. the pass gate transistors that couple bit lines to memory cells in an SRAM) may change as the supply voltage falls. The changed resistance may impact the ability to overdrive the memory cell for a write. Accordingly, the “trip point” (the point at which a write to a memory cell occurs) as a percentage of the supply voltage worsens as the supply voltage is decreased. Similarly, the ability to quickly and/or reliably read the memory decreases.